I personally would not recommend introducing a fish to an outdoor pond at this time of year with out weather. Spring is normally the best time. Can he hold off until March or April for the move?
If it is really desperate that he has to move, pick a sunny day with no ice on the pond surface. Get a fish bag and pop him in it with some of his tank water. And like any other acclimatising process, leave it to float to reach temperatures, and add a little pond water every so often to the bag.
How deep is your pond concord? For the warmest parts of England we need at least a 2 foot depth for fish to over-winter. If you’re from further up North, your pond will need a depth of 3 foot roughly for the fish to do okay.
Also be aware that this time of year, pond fish don’t eat very much at all. You will not need to feed him once introduced to the pond, as the cold temperatures puts them in a sort of hibernation. You might know all that already, but just throwing it all in.